A Coupled Torsion Beam Axle (CTBA) suspension system is often used as a rear wheel suspension system for small vehicles, due to its weight, cost and operation. As shown in FIG. 1, trailing arms 2 are welded to both ends of a torsion beam 1 extending in a lateral direction of a vehicle. One end of the each of trailing arms 2 is coupled with a vehicle body by a bolt with a bush 3 therebetween, and the other end is connected to a wheel 4 (only one of which is shown, for clarity). A torsion bar is inserted into torsion beam 1, and each end of the torsion bar is connected to one of the trailing arms 2.
A spindle bracket 5 is attached to the wheel-side end of each trailing arm 2. The wheels are connected to the trailing arms through the spindle brackets. A spring seat 6 is attached to the wheel-side end of the trailing arm so as to face the inside of the vehicle body. A suspension spring 7 is seated on and supported by the spring seat, and the other end of the suspension spring is connected to the vehicle body.
A typical spindle bracket 5 includes two vertical flanges, a horizontal flange, and a circular assembly hole into which a spindle coupled with the wheel 4 is inserted. The flanges are welded to the trailing arm.
Load applied through the wheel is transmitted to the torsion beam through the spindle bracket. The magnitude of the vertical load is three times as large or more as that of the lateral or longitudinal load.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.